2009-10-28

Opportunity Sol 271 (Spirit Sol 292)

I arrive a little early so that I'll be there when the downlink starts to flow. I'm a little anxious about the drive, yet confident.

While we're waiting around, Eddie Tunstel asks me a question. "I was looking over your uplink report from yesterday and noticed something about the starting position. It doesn't seem to match what we have in the telemetry."

Suddenly I don't feel so well. I look back at my notes and realize that I must have used the wrong INCONS (initial conditions) file for planning this drive. The file I used matches the one before the most recent drive, so it starts the simulated rover about 3m away from Opportunity's true position. Which could be very, very bad.

Luckily, the more I look into it, the more it looks as if we dodged a bullet. What we needed in order for this drive sequence to execute successfully was (a) that we start out at a 25-degree heading, and (b) that there be lots of room behind us. It so happens that we had a 25-degree heading in the INCONS file I loaded, just about exactly Opportunity's actual heading (or else we'd have been more likely to catch the error). And we checked imagery to establish that there was free space behind us, and that's not affected by the choice of INCONS file.

The only thing that might screw us up is that we chose the rover's starting position to establish a 10m-radius "safety zone" for the drive -- if we left that zone, the rover would stop driving. But since our true starting location was only about 3m away from the one we were using in planning the drive, we're still likely to stay within the zone for the whole drive.

Or so I hope.

Still, I get more and more nervous as more and more time goes by with no data. The SOWG meeting starts and we still have nothing from the spacecraft -- half an hour late, without so much as a byte on the ground. I can't help it. I start thinking of ways that using the wrong INCONS might have killed the rover.

Of course, it turns out Opportunity is just fine. Our problem's not with Opportunity, it's with Spirit. Both rovers are sending thisol's downlink via Odyssey, and Spirit got in ahead of us, with a whopping 148 Mbits -- all of which has to come down before we get anything from Opportunity. And there's hardly anything we can do before we get that data.

So we take a couple of hours off ....

When the data does arrive, it brings good news. It's about time we had some good news! I'd almost forgotten what it looks like. In this case, it looks like a front (downhill-facing) HAZCAM image showing switchback tracks downhill of us. We made some progress uphill!

Happily, Justin Maki made sure every image file that comes from the spacecraft includes metadata saying, among other things, where the image was taken, so we know just about exactly where the rover is. Turns out we made about 4.25m of total distance from our starting point (our actual starting point, not the wrong one I was using). About 3.5m of that is uphill motion.

It may not sound like much, but I'm practically ecstatic. The 3.5m itself is good news, but even better, it means we've got a technique to make more uphill progress whenever we want to.

About then the data stops coming. There's hope of more later, but it won't arrive for a while, and most people are still out to lunch and stuff, so I tell them to call me if anything interesting happens, and I go off and have a long talk with John Wright about what we need to do to adapt RSVP for Phoenix.

When that's over, I head back upstairs and -- oops. I guess everybody wasn't out to lunch and stuff. Frank has the next sol's drive pretty much ready to go, and Saina's pushed the process up to the activity plan approval meeting already and is ready for the walkthrough.

Well, that's embarrassing, but it's not enough to put a damper on my mood. My mood is further bolstered by the traversability meeting that follows, which has pretty much the same participants as a couple of sols ago, but now they're not so sure we can't make it to Burns Cliff.